The present invention relates to a flexible laminate used as a packaging material for electronic parts such as TAB and COF, and in particular relates to an adhesive-free flexible laminate.
An FCCL (Flexible Copper Clad Laminate), in which metal conductor layers primarily formed from copper are laminated on a polyimide film, is broadly used as a circuit board material in the electronics industry. Among the above, an adhesive-free flexible laminate substrate (particularly a two-layer metalizing laminate) that does not include an adhesive layer between a polyimide film and a metal layer is a material that is catching attention on demand of finer pitches of the circuit wiring width.
As a method of producing a flexible laminate substrate; particularly an adhesive-free flexible laminate substrate capable of accommodating fine pitches, primarily performed is a so-called metalizing method of forming, in advance, a tie-coat layer configured from a material having favorable adhesion with polyimide on a polyimide film by a drying method such as sputtering, CVD, or vapor deposition and a metal seed layer as a conductor of the cathode/current in the subsequent electroplating process, and thereafter forming a metal layer film to become the conductor layer of the circuit board by way of electroplating (refer to Patent Document 1).
In this metalizing method, in order to increase the adhesion between the metal layer and the polyimide film, modification is carried out by performing plasma treatment to the polyimide film surface in order to eliminate the contaminants on the surface and to improve the surface roughness prior to forming the metal layer (refer to Patent Document 2 and Patent Document 3).
Generally speaking, in the metalizing method, when pre-forming a metal layer on a polyimide film by a dry plating method such as sputtering, the improvement of adhesion and etching properties is being sought through the selection of the interlayer material (refer to Patent Document 4). Moreover, proposed is technology of sputtering a material selected from nickel, chromium, molybdenum, tungsten, vanadium, titanium and manganese on a polyimide film, subsequently sputtering a copper layer of approximately 50 nm, and further electroplating a copper layer of 1 μm or more (refer to Patent Document 5).
If copper and polyimide come in direct contact in the FCCL (Flexible Cupper Clad Laminate) in which the copper and a film such as a polyimide film are bonded; it is well-known that the peel strength will deteriorate. Thus, proposals have been made, as with Patent Document 6, to provide between the organic film and the copper layer an intermediate layer (tie-coat layer) possessing superior bondability with an organic film and which is capable of inhibiting the diffusion of copper.
However, the peel strength still deteriorated even with a tie-coat layer for inhibiting the diffusion of copper, and it was necessary to determine the cause thereof.    [Patent Document 1] Japanese Patent No. 3258296    [Patent Document 2] Japanese Patent No. 3173511    [Patent Document 3] PCT (WO) 2003-519901    [Patent Document 4] Japanese Published Unexamined Patent Application No. H6-120630    [Patent Document 5] Japanese Published Unexamined Patent Application No. H7-197239    [Patent Document 6] Japanese Published Unexamined Patent Application No. H9-083134